"It is a sustained campaign, not a series of isolated incidents," she said in a speech to a small audience of academics Thursday, according to a transcript released by the spy agency on Friday. "Radicalizing elements within communities are trying to exploit grievances for terrorist purposes.

Officials are also "aware of numerous plots to kill people and to damage our economy," she said. "What do I mean by numerous? Five? Ten? No, nearer 30 that we currently know of."

"It's easy to pull out alarmist headlines," he said. "What we're seeing here on the whole are lone individuals (and) small groups."